1. Field of the Invention
The invention relates to a solar battery controller.
2. Description of Related Art
There is known a solar battery controller including a solar battery module of which an output voltage is increased by connecting a plurality of solar battery cells in series. In such a solar battery controller, when a light intensity applied to part of the solar battery cells of the solar battery module decreases because of the influence of a shadow, or the like, the part of the solar battery cells, to which the decreased light intensity is applied, can supply a decreased current. Therefore, a current flowing through the other solar battery cells also decreases to the current that the part of the solar battery cells to which the decreased light intensity is applied can pass, with the result that the amount of electric power generated by the overall solar battery module decreases. Therefore, by bypassing the solar battery cells decreased in power generation capacity, the amount of electric power generated by the overall solar battery module is kept high.
A maximum output point of the solar battery module fluctuates depending on a weather condition, or the like, so control called maximum power point tracking (MPPT) for maximizing electric power generated by the solar battery module is executed. In MPPT, for example, the maximum output point of a P-V characteristic curve (power-voltage characteristic curve) is searched for by hill-climbing method. In MPPT, usually, it takes a time of about several seconds to several tens of seconds to obtain the maximum output point.
Incidentally, when the solar battery module is installed on a moving object, the amount of solar radiation varies in a short cycle (for example, about several tens of milliseconds) because of movement of the moving object. When the P-V characteristic curve significantly fluctuates as a result of bypassing the solar battery cells decreased in power generation capacity as described above, there is a possibility that it takes time more than usual to obtain the maximum output point in MPPT or the maximum output point cannot be found.
That is, when the solar battery module is installed on the moving object, it is not possible to track a variation in the amount of solar radiation in a short cycle even with a combination of the MPPT with the method of bypassing the solar battery cells decreased in power generation capacity. As a result, the amount of electric power generated by the solar battery module may remarkably decrease while the moving object is moving.